This invention relates to light sources, especially those applied to luminaire systems. It is particularly useful in providing a uniform illumination source whose luminosity can be controlled, or for coupling light into one or a plurality of optic fibres.
The aim of any light source is to collect as much light as possible that is emitted from a bulb, and to direct this light into the chosen direction. This has traditionally been achieved using a reflector behind the bulb to collect the light that is emitted backwards or sideways, and to reflect this light into a forward direction. The reflector is acting as an imaging optic, providing a (blurred) image of the bulb filament in the forward direction.
The light source described in this invention does not image the bulb filament, but scatters the emitted light within a chamber. The chamber is arranged to have an exit means for the scattered light to escape, and thus provide an output. The principle is similar to that used for integrating spheres. Here a light source is placed inside a sphere whose interior is coated with an efficient reflective or scattering material. Typical efficiencies are  greater than 99% for the incident light being reflected or scattered, which means that very little light is absorbed by the inside surface of the sphere. The light emitted from the light source is thus scattered many times within the sphere, effectively randomising the direction of travel of the photons. Any particular portion of the inside of the sphere will have the same light power incident upon it. When a small light detector is placed at the surface of the sphere, the reading on the detector will be proportional to the total amount of light emitted from the source, independent of the direction that it was emitted in. This type of photometric analysis is the usual application of these devices.
It is an object of this invention to use an efficient scattering chamber as a uniform illumination light source.
According to the present invention, there is provided apparatus comprising:
a light source;
a scattering chamber having an internal surface for scattering light from the light source; and
an exit port in the chamber which provides a light output.
By this invention, the exit port emits a uniform light intensity, independent upon the directional properties of the light source, e.g. an emission light bulb. In other words, a non-imaging light source is provided in which any information about the spatial distribution of the light emission is removed by multiple scattering events as the photons pass across the inside of the chamber.
The light source can be any of the following:
a) Fluorescent light, linear and compact
b) Halogen incandescent lamps
c) Incandescent light bulbs
d) Tungsten filament lamps
e) High intensity discharge (HID) lamps
f) Light emitting diodes (LEDs) all/different colours
g) Electroluminescent lamps
h) Radioluminescent lamps
i) Radiofrequency (RF) lamps
j) Microwave light sources
k) Laser light sources
The light source may consist of one or more light emitters positioned internally and/or externally of the chamber. Where more than one emitter is provided, these may be the same or different. Where an external emitter is provided, the chamber has an entrance port for light to enter the chamber. More than one entrance port may be provided.
The chamber may be adapted to reduce heat build-up within the chamber and/or in the light output at the exit port. For example, one or more windows may be provided with reflective/transmissive properties for separating visible light and infrared radiation (heat). Thus a window may be provided in the chamber wall to transmit infrared radiation out of the chamber and reflect visible light within the chamber and/or a window may be provided in the exit port to transmit visible light out of the chamber and reflect infrared radiation within the chamber.
The intensity of the light output may be controlled by varying the intensity of the light source. This may be achieved by mechanical, electrical or electronic systems. A mechanical system may employ an adjustable shutter for covering the light source. This is particularly simple and can take various forms, for example, a sliding cover or an iris diaphragm. More than one exit port may be provided.
Specific embodiments of the invention will now be described by way of example, with reference to the accompanying drawings.